In the past, radar antennas and other sensors which must locate a target at any point within a field of view have often been mounted on multi-gimbaled platforms. In an arrangement of this sort, two gimbals, rotatable about perpendicular axes, are driven by servomotors to scan an area and align the sensor with a detected target. The system requires that the servos be driven by a controller that generates a preprogrammed sequel of commands or generates necessary commands based on some feedback system. While used extensively, multi-gimbaled arrangements of this sort are not altogether satisfactory since they require precisely calibrated electrical torquers to maintain knowledge of sensor direction and position and also require a complex controller to determine the fractional motion by each servo. The most significant disadvantage, however, is the required precision of the device and its associated cost, weight and complexity.
Other attempts at mounting radar antennas and the like have used azimuth/elevation or generically similar mounts. These employ an azimuth drive for alignment in the reference plane and an elevation drive which positions the sensor at an angle measured from the reference plane to the line of sight of the sensor. These systems, however, still require at least one gimbal and the use of precision gearing with anti-backlash provisions, making them bulky and expensive.